In FIG. 1a we show, in schematic cross-section, a typical magnetic write head of the prior art. It is made up of lower pole 19 (P1) which is connected to upper pole P2, on one end at back-gap 17 and at the other end through write gap 13. A write coil (not shown) is located within chamber 18. When the write coil is energized by passing a write current through it, a magnetic field is generated, the flux from this field being constrained to lie almost entirely inside P1 and P2. The only exception is at gap 13 across which the full flux passes. Fringe fields from the flux passing across gap 13 extend out as far as recording media 14 and interact with it. P2 is made up of yoke 11 which terminates at pole tip 12.
FIG. 1b is a plan view of the left hand portion of FIG. 1a, making FIG. 1a a cross-section of FIG. 1b taken through 1a—1a. As can be seen, the yoke starts out relatively wide where it is well removed from pole tip 12 and, as it approaches the latter, its width is gradually and uniformly reduced until flare point 15 is reached where the width stays constant, defining the area covered by the write pole and thus the width of the write field at the surface of the media.
To be able to accommodate increases in the recording density, media coercivity must be increased to overcome the demagnetization field of the magnetic transition. However, as the track width decreases, the head field strength tends to decrease due to saturation of the pole tip. Unfortunately, a high-end hard disk drive (HDD) generates such a high data rate transfer that not only is greater head field strength required, but there also is a need for a faster flux rise time.
So as to attain a large enough overwrite (OW) value, the write current is boosted, giving its waveform a large overshoot. This often brings about severe excess saturation of the media, and the recorded transition quality degrades. As a result of this readback pulse width broadening, nonlinear transition shifts, media noise increases, and adjacent track erasures often occur.
A routine search of the prior art was performed with the following references of interest being found:
In U.S. Pat. No. 6,493,191, Gain et al. describe a recording head where the dimensions of the yoke are designed to avoid saturation at the pole tips during writing. U.S. Pat. No. 6,473,276 (Chang et al.) discloses a notch at the flare point of the yoke. U.S. Pat. No. 6,339,523 (Santini) shows a flare point close to the air bearing surface of the write head while, in U.S. Pat. No. 6,288,871, Tanabe shows the width of the yoke shorter than the magnetic gap width